二维数组的排序可以利用Comparator接口来实现。

        int[][] graph = new int[100][2];
        for(int i = 0;i < 100;i++){
            graph[i][0] = (int)(Math.random() * 1000);
            graph[i][1] = (int)(Math.random() * 1000);
        }
        Arrays.sort(graph, new Comparator<int []>() {
            @Override
            public int compare(int[] a, int[] b){
                if(a[0] == b[0])    return a[1] - b[1];
                return a[0] - b[0];
            }
        });
        for(int i = 0;i < graph.length;i++){
            for(int j = 0;j < 2;j++){
                System.out.print(graph[i][j] + " ");
            }
            System.out.println();
        }